Etching method and method for forming contact opening

Abstract

An etching method is described, including a first etching step and a second etching step. The temperature of the second etching step is higher than that of the first etching step, such that the after-etching-inspection (AEI) critical dimension is smaller than the after-development-inspection (ADI) critical dimension.

Description

BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to an etching method. More particularly, the present invention relates to an etching method capable of reducing critical dimension (CD), and to a method for forming a contact opening that utilizes the etching method. [0003] 2. Description of the Related Art [0004] As the integration degree of IC is always required to be higher, the dimension of semiconductor devices unceasingly gets smaller. In the prior art, the miniaturization of pattern pitch in IC fabrication is mostly made by enhancing the lithographic resolution. However, high-resolution lithography techniques are more difficult and expensive due to the limitations of optics. [0005] Instead of enhancing lithographic resolution, the critical dimension of pattern after etching can be reduced alternatively by modifying the etching process. In the modified etching method, a patterned photoresist layer with an after-development-inspect...

AI Technical Summary

Benefits of technology

[0006] In view of the foregoing, this invention provides an etching method that is capable of reducing the after-etching-inspection (AEI) CD.

[0007] Another object of this invention is to provide an etching method that is capable of reducing the critical dimension of patterns to increase the integration degree of IC.

[0008] Still another object of this invention is to provide a method for forming a contact opening, which is capable of preventing bridging between adjacent contact plugs to improve the reliability of semiconductor devices.

[0023] The etching method of this invention is capable of forming a protective layer on the top surface of the patterned photoresist layer and a spacer on the sidewall of the same, so that the photoresist loss in the etching steps can be reduced, and the opening expansion problem can be avoid so that the after-etching-inspection (AEI) CD is smaller than the after-development-inspection (ADI) CD. Therefore, the CD of the devices can be reduced effectively. It is particularly noted that adopting the etching method of this invention can also improve the etching selectivity effectively.

[0024] Since the method for forming a contact opening of this invention can prevent the opening expansion effect, adjacent contact openings will not overlap with each other to cause bridging between adjacent contact plugs. Therefore, the reliability of the devices can be improved.

Problems solved by technology

As the integration degree of IC is always required to be higher, the dimension of semiconductor devices unceasingly gets smaller.

However, high-resolution lithography techniques are more difficult and expensive due to the limitations of optics.

However, since an opening in the photoresist layer and the anti-reflection coating (ARC) is easily expanded in such an etching method, the CD of the corresponding opening in the etched layer cannot meet the requirement.

On the other hand, the above etching method has a limitation on the extent of CD reduction and may cause a striation effect, upon which the top-view profile of the openings is much changed so that adjacent openings overlap with each other to cause bridging between adjacent contact plugs.

Therefore, the reliability of the devices is lowered.

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